MgSO4.7H2O is a hydrogen bonded crystal having wide application in various fields.Urea and thiourea (as organic additives) were added (separately) into the MgSO4.7H2O solution in different molar ratios and single crystals were grown by the free evaporation method at room temperature. The grown crystals were characterized structurally, chemically, thermally, optically, mechanically and electrically. The densities and lattice volumes observed indicate that the impurity molecules have entered into the host crystal matrix. All the eleven crystals grown are thermally stable upto about 70°C. Lower concentrated urea and higher concentrated thiourea additions are found to improve the optical transmittance. Results of microhardness measurements follow the normal indentation size effect. Results of electrical (AC and DC) measurements indicate that the grown crystals exhibit a normal dielectric behaviour and the electrical conduction is understood to be due to protonic movement. The present study indicates that urea/thiourea addition plays an important role in reducing the dielectric constant (εr) value significantly to make MgSO4.7H2O crystal a lower value dielectric material, expected to be useful in the microelectronics industry.